With the development of science and technology, various electronic products emerge and are almost indispensable in daily life. With advantages of high energy density, long cycle life, environmental friendliness and reproductively, lithium ion batteries have been widely used in various electronic products.
In the related art, a separator is generally used to isolate an anode current collector from a laminated aluminum film. Since the requirements of energy density of an electric roll at the market become higher and higher, a thickness of the separator, a thickness of the polypropylene layer on the laminated aluminum film, and a thickness of the anode current collector become smaller. In one aspect, anti-puncture strengths of the thinned separator and polypropylene layer become lower. In another aspect, since the anode current collector of the lithium ion battery is a copper foil, with the restriction of process conditions in the related art, burrs may present on an end edge of the copper foil, which may cause the case where the burrs on the end edge of the anode puncture the separator and the laminated aluminum film under extreme conditions. However, when the electric roll is formed by winding, corners on two side faces of the thinned anode current collector will become sharper, which increases the probability that the separator and the polypropylene layer of the laminated aluminum film are punctured by the anode current collector. In the related art, the method for isolating the anode sheet from the laminated aluminum film by using the separator is hard to ensure good isolation effects.
The separator and the polypropylene layer of the laminated aluminum film are punctured, which may cause battery leakage, and more seriously may result in that the anode is conducted with the aluminum foil layer via contact. In this case, an electrochemical reaction may occur and thus the polypropylene layer of the laminated aluminum film may be subjected to corrosion, which also causes battery leakage and corrosion.